You might not expect evangelical Christians to get involved in a political fight over mercury regulations. But when the Environmental Protection Agency proposed in March to tighten limits on industrial mercury emissions, the move caught the attention of an influential group of religious environmentalists who are now butting heads with pro-business Republicans seeking to weaken the regulations in the House on Friday afternoon.

The EPA says its rule would reduce mercury emissions from coal-burning power plants by more than 90%, and also sharply restrict acid gas and sulfur dioxide emissions. The plan delighted leaders of the growing evangelical environmentalist movement, which argues that humans have a Biblical mandate to protect nature. Of particular significance to pro-life evangelicals is the impact the rule could have on unborn children. Medical experts have long warned that high mercury levels in fish like tuna and swordfish can cause pre-natal brain damage and neurological disorders.

Not all Republicans in Congress have met the EPA’s rules with open arms, however. The House will vote today on the TRAIN Act, a bill that creates a committee to determine whether the cost of proposed EPA regulations, including its latest mercury standards, is worth the benefit. Republicans argue that a weak economy is not the time for potentially costly changes. Chairman of the House Subcommittee on Energy and Power, Rep. Ed Whitfield of Kentucky, proposed in July to wrap mercury regulations into this yearlong review. “What I have proposed is that we go forward with regulations that are reasonable and workable but which allow a little more time for compliance, so as to temper the job loss impact as well as the increased costs on electricity consumers,” he explained to TIME. Michigan Rep. Fred Upton and Joe Barton of Texas have supported the delay on similar grounds. Alaska Senator Lisa Murkowski also sent a letter to the EPA on Sept. 8 asking them to hold off on their regulations, citing energy price increases if non-compliant power plants are forced to close. Since the Federal Energy Regulatory Commission has yet to verify the EPA’s findings, her energy spokesman said, delay is imperative.

Yet this delay faces strong opposition from the rule’s supporters, including evangelicals who argue that mercury pollution is an immediate crisis for the unborn. At the forefront is the Evangelical Environmental Network, a coalition of religious leaders that calls its work “grounded in the Bible’s teaching of the responsibility of God’s people to ‘tend the garden’” of Earth. The group’s leader, Rev. Mitch Hescox, is a registered Republican who worked in the utility and coal industries for 14 years before becoming a pastor.

Taking the fight to Republican critics of the EPA move, the EEN is mounting an ad campaign targeting Republicans Whitfield, Upton and Barton for opposing mercury restrictions while running on pro-life platforms. “I expect members of Congress who claim that they are pro life to use their power to protect the life, especially the unborn,” says a local pastor and mother in one of the ads. “I can’t understand why Congressman Ed Whitfield is fighting to stop the EPA from enforcing its plan specifically meant to protect the unborn by cleaning up dangerous mercury pollution.” The ads have run on 120 Christian and country radio station in Whitfield, Barton and Upton’s districts for the week prior to the Train Act vote. More than 100 evangelical pastors and leaders have also signed the “Evangelical Call to Stop The Mercury Poisoning of the Unborn,” including representatives from over 10 Christian colleges, National Association of Evangelicals President Leith Anderson and Christianity Today’s Editor-in-Chief David Neff. The United States Council of Catholic Bishops submitted similar concerns. “A national standard limiting mercury and other toxic air pollution represents an important opportunity to protect the health and welfare of all people, especially our children and poor and vulnerable communities,” wrote Bishop Stephen Blaire. “While there are short-term costs involved in implementing this standard, the health benefits of such a rule outweigh these costs.”

Supporters of the regulations cite studies that jobs and costs are not at stake if the regulations go into effect as the EPA hopes. An analysis by the left-leaning Economic Policy Institute analysis shows the toxins rule would create a net 28,000 to 158,000 jobs over the next four years; the Political Economy Research Institute at the University of Massachusetts puts the overall estimate even higher at 1.5 million in positions associated with the new pollution controls. The EPI also argues that the new standards could save $55 billion to $146 billion per year in health costs, dwarfing the $11.3 billion annual cost of imposing the regulations. Some inside the industry also agree the rules should pass soon. Over 30 energy companies, including PSE&G and National Grid, urged Congress in a July 11 letter to follow the EPA’s regulations. Concerns about the industry’s ability to implement new standards are, they say, “based on assumptions that underestimate the ability of America’s electric sector to invest, retrofit, and construct new clean generation.”

Even so, some of the Republicans under pressure are suspicious of the EEN’s motives. “This is an activist environmental group parading under the banner of evangelical Christianity and the right to life,” Whitfield’s chief of staff John Sparkman told TIME. “I don’t think it will have resonance in our district.”

The latest guess is that the TRAIN Act will pass. Evangelical supporters of the regulation hope that a little help from President Obama might tip the balance. In his Sept. 8 jobs speech, Obama specifically referenced the issue: “What I will not do is let this economic crisis be used as an excuse to wipe out the basic protections that Americans have counted on,” Obama said. “I reject the argument that says for the economy to grow, we have to roll back […] rules that keep our kids from being exposed to mercury.” While environmentalists complain that Obama is yielding on other fronts to pressure from big business–earlier this month the president halted a planned EPA ozone smog-reduction regulation–the White House affirmed its position on Wednesday with a vow to veto the TRAIN Act if it passes Congress.

That’s thrilling news to pro-life evangelical leaders who differ with Obama on plenty of other issues, including abortion and stem cell research. But on this issue, Obama and evangelical environmentalists agree that, as the EEN’s Hescox argued, the pro-life position requires protecting children and the unborn from industrial pollution. “‘Let the little children come to me, and do not hinder them, for the kingdom of God belongs to such as these,’” Hescox said, quoting the Bible with emphasis. “We are denying our children a full and abundant life by threatening them with mercury.” If the bill passes the House on Friday, that’s a message Hescox and his allies are sure to bring to what they hope will be a more receptive Democratic-led Senate.

Update, 1:32 p.m.

The TRAIN Act passed the House on Friday afternoon 249-169. The bill, subject to Senate approval, would create a committee to analyze the impact of the EPA’s rules.